SD cafd read only

[jd1008]

On 05/16/2015 06:06 PM, Peter Skensved wrote:
>>
>> On 16/05/15 17:36, Joe Zeff wrote:
>>>> I really believe this thing has failed.
>>> You're probably right.  Still, before tossing it, if toss it you must,
>>> what do you get from this:
>>>
>>> fdisk -l /dev/sdh
>>>
>>> Does that show the full size, or just the 3.9GB?  If nothing else, we
>>> might learn something about the card's failure modes.
>>> -- 
>> .
>> [root at box10 /]# fdisk -l /dev/sdh
>> Disk /dev/sdh: 3.7 GiB, 3906453504 bytes, 7629792 sectors
>> Units: sectors of 1 * 512 = 512 bytes
>> Sector size (logical/physical): 512 bytes / 512 bytes
>> I/O size (minimum/optimal): 512 bytes / 512 bytes
>>
>> Just the 3.9GB, the other 12 is not accessible.
>>
>
>    Are you sure this is really a 16GB card ? Lots SD cards and USB cards ( even
> branded ones ) are fake and do not hold anywhere near the stated capacity. You
> may want to try to run f3write / f3read ( from http://oss.digirati.com.br/f3/ )
> on it to see what the actual capacity is.
>
>   With a fake card everytig works well until the real capacity is filled at which
> point it just keeps overwriting itself until completely scrambled.
>
>   The kernel will usually react to this by remounting it read only.
>
>                                          peter
That's not necessary.
All he has to do is read the card via dd like so:
dd if=/dev/sdX (X=[b,c,d,e,f,...etc] of=/dev/null bs=4M

dd will then state how much it read.